Why sodium
hydroxide based
chemicals should not be used to clean roofs
Roof cleaning is a trade that requires special equipment and knowledge to
insure that it is being cleaned safely, and that you are getting the
results that you want, and deserve. It is important that only non pressure
roof cleaning methods be used on asphalt shingles.
Did you know that most of the roof cleaning chemicals that are sold at the
bigger box stores, and certain ones sold at other local suppliers contain
sodium hydroxide? If you are unfamiliar with what sodium hydroxide is it
is a very strong caustic chemical that is widely used as a degreaser in
many industries. The reason this is such a problem when used for cleaning
roofs, is that asphalt roofs are a petroleum based product and logic says
using a degreaser on something held together with grease is probably not a
good idea. It can, and probably will, degrade the asphalt holding the
shingles together.
Here are a few other disadvantages that make sodium hydroxide based
chemicals a bad choice for asphalt shingle roof cleaning:
Too much pressure – Once these chemicals have been applied, they
will require at least 400-500 psi of pressure to insure enough agitation
to the roofs surface to successfully remove the top layer of algae which
can also loosen and remove the granules that are embedded in the asphalt.
Roofs that are properly cleaned, using the right cleaning mixtures, should
not require any agitation, or pressure, for the algae to be removed
successfully.
Sodium hydroxide does not kill the algae that is growing on the roof
– Rather it simply works as a surfactant to loosen and remove the top
layer of visible algae, while traces of living algae and the algae spores
remain intact and ready to re infest the roof top. That's why after
cleaning with these chemicals, even though the roof may appear clean, you
will usually see visible re-growth within as little as 3-6 months. When a
roof is cleaned correctly, even with the conditions we experience here in
Jacksonville, Florida, it can stay free of any visible algae for as long
as 2-4 years.
Risk to painted surfaces – because of the strength of mixtures
needed for a sodium hydroxide based chemical to be affective at removing
the top layer of algae on a asphalt shingle roof, it can put painted
surfaces such as painted exterior sidings, painted roof vents, stained
fences in close proximity to the house, etc at risk of being damaged by
way of stripping. In fact, sodium hydroxide is a common main ingredient in
many chemicals designed for stripping wood finishes such as stains and
sealers.
As you can see there are many disadvantages to using these kinds of
chemicals for cleaning asphalt shingle roofs. They are manufactured simply
because they are cheap to produce, and stable on a shelf for long enough
to sell for big profits. Also, because these products are fairly safe to
use around landscaping, these sodium hydroxide based products are an easy
marketing tool for an inexperienced contractor or do-it-yourselfer. The
fact is, roof cleaning isn't easy, and shouldn't be attempted by
homeowners or anyone else that doesn't have the proper knowledge,
experience, and equipment to make sure it gets done the right way, and the
safe way.
